Originating in Europe during Victorian times, pie funnels were simply hollow ceramic funnels placed in the center of a pie to allow steam to escape during baking. The decorative bird shapes came much later. It is unclear if the reason for bird shapes came from the nursery rhyme “Sing a Song of Sixpence”..... “four and twenty blackbirds baked in a pie”.
Pie birds are usually looking up to the sky, and you can sometimes hear the steam escaping from its beak giving the impression the bird is singing. As an added benefit, pie birds act as support for the top crust to prevent sagging. Since the 1940's pie birds have been manufactured in various designs and styles.
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